Angle-of-lead control



CER 293569189 5R W. F. TUFTS ANGLE-OF-LEAD CONTROL Aug. 22, 1944.

Filed NOV. 24, 1942 Search Room 33. GEOMETRHSAL His! Hummm;

Patented Aug. 22, 1944 Search Room UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) 6 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to re control devices,

and more particularly, to such devices whose function it is to adjust the gun sight for the proper lead or angle of lead. The axis of bore of the `gun to be aimed does not turn in angular unison with the line of sight of the sighting device; provision is made, between the angle through which the gun (axis of bore) is turned and the angle through which the sight line of sight is turned, for introducing the angle of lead to compensate principally for movement of the target. The amount of lead required depends chiefly upon the rate of movement of the target and its distance from the gun or range.

It is the object of this invention to devise a mechanism for compensating for lead, adjustable both as to the rate of movement of the target and its range, Which may be facilely applied to existing equipment, between the gun mount and the sighting mechanism, and which will function fully automatically without the need of manual adjustments or calculation of data on the part of the gunner. For the attainment of these objects and such other objects of invention as may herein appear or be pointed out, I have shown an embodiment of my invention in the accompanying sheet of drawing, wherein:

Fig. 1 is an isometric view of the improved angle-of -lead control in cooperative position relative to the gun mount and the sighting mechamsm;

Fig. 2 is an isometric view of a two-frame gyroscope, as an aid to the explanation of the underlying principles of this invention; and

Fig. 3 shows, also isometrically, a fragmentary portion of the device of Fig. 1, particularly the panoramic telescope and its connection to the gyroscope, for tracking in elevation.

The gun barrel l the axis of bore of which is designated B-B is mounted on horizontal trunnions 2 to provide for elevational adjustment, and journalled in upper carriage 3, which is itself mounted on main carriage 4 for angular adjustment in azimuth about the vertical spindle 5. The handwheel 6a, worm 6b and segmental worm Wheel 6c are used for moving the gun in azimuth on axis 5. The improved lead control will be illustrated in connection with a target moving in a horizontal plane (azimuth) in which case the gun l might be considered to be secured in upper carriage 3 without the elevational adjustment alforded by trunnions 2, although it is to be understood that the device may as readily be applied in connection with a target moving in a vertical plane (elevational lead).

The sighting mechanism is illustrated in the form of a panoramic telescope, by which is meant a telescope in which the objective piece, designated II in Fig. 1, may be adjusted relative to the eye piece, designated I0. As shown in Fig. 1, objective piece II is angularly adjustable, in azimuth, about a vertical axis T--T' relative to eye piece IU which is secured and mounted on the upright post 9. The panoramic telescope is provided with an optic systeml which reflects light entering objective piece Il on line ST, vertically upwards on line TT to be again reflected to a horizontal line (T-S) through eye piece I0; the lines S-T, T-T' and T-S' all lie in the same vertical plane. The line of sight is thus STTS. The upright post 9, Which also supports the adjustable objective piece Il, as clearly seen in Fig. 1, is mounted on a horizontal bracket 1 which extends from and is supported on upper carriage 3 so as to turn in azimuth with the gun, so that the sighting telescope Ill-II moves with the gun I about the pivotal axis 5. Where it is not necessary to compensate for lead, the objective piece Il may be made xed relative to its eye piece I0, in which case the line of sight S-S, or, more accurately, STT'S, Will be maintained in parallel relation to the axis of bore B--B of the gun as the gun and sighting telescope are moved by handwheel 6a, as already described.

However, to introduce lead compensation the objective piece Il is mounted to turn relative to the eye piece Il) on vertical axis T-T' and is caused to be turned by the improved angle-oflead control, which will now be described. As stated above, angle of lead depends primarily on two factors, viz., rate of target movement and the range of the target. I have discovered that both factors can be taken into account by the use of a gyroscope as one part of my improved angleof-lead control. But before describing its functions therein, some of the principles of the gyroscope necessary to an understanding of my invention will rst be expounded, with the aid of Fig. 2.

Let the gyroscope wheel a, whose axis is mounted in the frame b, be rotating in a counterclockwise direction as is shown by the arrow c. The frame b is mounted in the frame d and is free to rotate about the horizontal axis X-X. The frame d is free to rotate about the vertical axis Z-Z. The law governing the gyroscope states that if a force is applied to a gyroscope, rotating about its axis Y-Y, causing it to rotate about an axis X-X, the resulting motion will not be in the direction of the applied force about the axis X-X, but will be about some other axis Z-Z, in order that coincidence may be established between the axis Y-Y and the axis X-X; and the direction of the motion about the axis Z--Z will be such that when coincidence is established, the direction of rotation of the wheel will be the same as that of the applied force.

Therefore, if a downward force F is applied to the frame b the frame b will not rotate about its axis XX. But the outer frame d will rotate about its axis Z--Z in a counterclockwise direction. Now since the axis Y-Y will chase, but never catch, the axis X-X, this counterclockwise motion about the axis Z-Z will continue as long as the force F is applied and as long as the wheel a continues to rotate. This rotation about the axis Z-Z is called precession. It is inversely proportional to the moment of inertia I and the rotational velocity w of the gyroscope, and directly proportional to the force F multiplied by its lever arm 1', which product is the torque T. Expressed as an equation. where p equals the rate of precession: pzT/I W. Where there is precession of a gyroscope, there must be an accompanying force. So that, if the gyroscope is caused to precess in a counterclockwise direction about the axis A--A by the application of a suicient force F at e', the frame b will lift up at e in an effort to establish, through the friction of the bearings X-X, the necessary accompanying force. Now if a spring were attached at e as is done at s in Fig. 1, the

`distance through which the point e would move up, for the given characteristics of the spring jand the moment of inertia I of the gyroscope,

would be dependent upon the rate of precession p caused by the force F at e' and upon the rotational velocity and the moment of inertia I of the gyroscope.

On the horizontal bracket 'l (of the upper carriage 3) I mount a one-frame gyroscope, comprising a gyroscope wheel 20 mounted by spindle 2| on frame 30 to turn in a counterclockwise direction shown by arrow c on axis 1l-y. Frame 30 is mounted on a pair of supporting posts 8 uprising from the horizontal bracket 1, for rotation on axis :v -x. The frame 30 is mounted on the said pair of posts 8 by means of a left trunnion 3l and a right shaft 32, journaled near one end in right post 8 and near its other end in the vertical support or post 9.

It is thus seen that the axes --cc and y-y of the gyroscope of Fig. 1 correspond with the axes of the gyroscope of Fig. 2, respectively X-X and Y-Y. Whereas the vertical axis Z-Z of the two frame gyroscope of Fig. 2 passes through the point of intersection of axes X-X and Y-Y, the vertical axis z--z of the single frame gyroscope of Fig. 1 does not pass through the corresponding point but is displaced to the left to coincide with the vertical spindle of uppercarriage 3. When the gun is traversed to the left, counterclockwise on axis z-z, shown by arrow u, precession is set up about z--2. For purposes of reference, the part at the muzzle will be termed the front, and the part at the breech, the rear. As explained in the discussion of Fig. 2, the frame 30 will turn about the axis .fc-:c in a direction to raise the front part, and to lower the rear part, of frame 3D. against the urgency of spring s. Frame 30 will continue to turn until a force is established to counteract the said precessional force, depending upon the rotational velocity w of the gyroscope and upon the rate of precession, that is, upon the rate of traverse of the gun.

Thus, the frame 30 will turn on axis m-r in direct proportion to the rate of traverse of the gun. As explained above, this is one of the two factors necessary to determine lead. The other factor is range; by correlating the rotational velocity of the gyroscope with range, the turning of frame 30 will account for both factors. This is done in the following manner: The motor 22 for driving the gyroscope is mounted on frame 30 and is operatively coupled to spindle 2|. The electrical circuit of motor 22 includes a resistance 23, calibrated according to the characteristics of the springs s and s', the moment of inertia I of the gyroscope, and other factors, into yards of range. The turning of frame 30 will now depend upon both range and rate of target movement; this movement is transmitted to the objective piece Il of the panoramic telescope by means of shaft 32 secured to the frame 3U, a pair of bevel gears 33--I3 and a short vertical spindle I 2 secured to the objective piece I l The leftward traversing of the gun, counterclockwise about z-e, shown by arrow u, will cause, as explained, an upward turning of frame 30, shown by arrow v, and shaft 32, and a clockwise turning, shown by arrow t, about axis T--T. Thus the line of sight is turned clockwise from STT'S to STT for a counterclockwise turning or traversing of the gun. Since the sight is trained on the target, this means that the gun will be turned an extra angle, the angle-of-lead, in a counterclockwise direction, i. e. to "lead the gun as is required in the case of a moving target. Moreover, the range having been estimated and set on the scale of rheostat 23 and the moving target tracked by the sighting telescope, which tracking or traversing movement (equal to the rate of target movement) is communicated to the gun and to the gyroscope mounted to move with the gun, the angle of lead of the gun will be the required one for the particular range and rate of movement.

The maximum angle through which frame 30 will be required to move, for any target velocity, will be relatively small. Therefore, in order to limit the movement of 30, while the target is being overtaken, the stops 35, 35 are provided. After the target is overtaken and the traversing rate is reduced for tracking, the spring s will return 30 to the proper angle.

As mentioned above, the invention is described in connection with azimuth tracking, in Fig. 1. Its application to elevation tracking would be similar, except that the orientation of the parts will be turned to that shown in Fig. 1; this is shown in Fig. 3 where the parts bear the same reference characters. In tracking a target moving in elevation, the gun must be compensated for the changing trajectory due to the gravity effect upon the projectile. This super-elevation is a constant amount and acts in the same, downward direction. Between the spindle 32 from the frame 30 of the gyroscope (see Fig. 1 for the continuation and connection of spindle 32) and the spindle 34 to which bevel gear 33 is secured, is a sliding-cam-sleeve coupling 40 having an axially oriented slot 42 in which is received a pin 32p on spindle 32 and a cam slot 44 in which is received a pin 34p on spindle 34. The coupling 40 is axially adjustable, as by 33'. Groupee/u msiiumms.

means of a forked lever 4I having pins received in an annular groove 40g of coupling 40. Lever 4| is adjusted in accordance with the range of the target, and may, if desired, be made to move with the rheostat arm 23 (Fig. 1), to shift the coupling 40 to cause its cam slot 44 to introduce an additional angular lead which depends upon range and which will compensate for superelevation.

I claim:

1. In re control apparatus for a gun mounted for traversing its axis of bore in azimuth about the train axis of the gun and provided With a pallilfiigj'ilcpe supported on the said gun mount with its eye piece xed to maintain its portion of the line of sight parallel to the said axis of bore, a` device for introduinagigle-of- @ad correction.betwetle'saidaxis of bore and tlisaid4 Alinefof sight'vdepending upon the apparent angular rate giltargemrgpvement and its range, comprising, in combinatinfalira'cket on the said gun mount for supporting the said panoramic telescope, a gyroscope having a single framamdunted on trai'bracket wititi'iiin axis whennot in operation, parallel to the said axis of bore and with its said frame horizontally disposed with its trunnions in a frame axis normal to the said spin axis and with its axis of precession coincident with the said train axis of the gun, a motor mounted on the said frame for rotating the gyroscope wheel, a pair of springs between the ends of the said frame and the said supporting bracket, one of the said frame trunnions serving as a shaft and operatively connected to the objective piece of the said panoramic telescope, whereby the traversing of the gun together with the said angle-of-lead device in azimuth tracking will cause a turning of the said frame on its said horizontal frame axis in response to the precessionalrlturning of the gyroscope, the said frame shaft transmittii`1"g"tl'retsaiid frame turning to the said objective piece of the panoramic telescope, whereby the line of sight is turned relatively to the said axis of bore depending upon the rate of azimuth traversinghawrheostat,in themcir- @Beelofmthe gyroscope Wheel""according to the range of nthem tracked target, whereby the said precessional eifetfth'e'said gun traversing, the said responsive frame turning, the said objective piece turning and the angularity of the said line of sight will be varied '1n proportion to range.

2. In re control apparatus for a gun mounted for traversing its axis of bore in azimuth about the train axis of the gun and provided with a panoramic telescope supported on the said gun mount with its eye piece xed to maintain its portion of the line of sight parallel to the said axis of bore, a device for introducing angle-oflead correction between the said axis of bore and the said line of sight depending upon the apparent angular rate of target movement and its range, comprising, in combination, a gyroscope having a single frame mounted with its spin axis parallel when not in operation, to the said axis of bore and with its said frame horizontally disposed With its trunnions in a frame axis normal to the said spin axis and with its axis of precession coincident with the said train axis of the gun, a motor mounted on the said frame for rotating the gyroscope wheel, one of the said frame trunnions serving as a shaft and operatively connected to the objective piece of the said panoramic telescope, whereby the traversing of the gun together with the said angle-of-lead Search Room device in azimuth tracking will cause a turning Iof the said frame on its said horizontal frame axis in response to the precessional turning of the gyroscope, the said frame shaft transmitting the said frame turning to the said objective piece of the panoramic telescope, whereby the line of sight is turned relatively to the said axis of bore depending upon the rate of azimuth traversing, a rheostat in the circuit to the said motor adapted to regulate the speed of the gyroscope wheel according to the range of the tracked target, whereby the said precessional effect of the said gun traversing, the said responsive frame turning, the said objective piece turning and the angularity of the said line o sight will be varied.' in proportion to range.

3. In iire control apparatus for a gun mounted for traversing its axis of bore in azimuth about the train axis of the gun and provided with a panoramic telescope supported on the said gun mount with its eye piece xed to maintain its portion of the line of sight parallel to the said axis of bore, a device for introducing angle-oflead correction between the said axis of bore and the said line of sight, comprising, in combination, a gyroscope having a single frame mounted with its spin axis parallel when not in operation, to the said axis of bore and with its said frame horizontally disposed with its trunnions in a frame axis normal to the said spin axis and with its axis of precession coincident with the said train axis of the gun, one of the said frame trunnions serving as a shaft and operatively connected to the objective piece of the said panoramic telescope, whereby the traversing of the gun together with the said angle-of-lead device in azimuth tracking will cause a turning of the said frame on its said horizontal frame axis in response to the precessional turning of the gyroscope, the said frame shaft transmitting the said frame turning to the said objective piece of the panoramic telescope, whereby the line of sight is turned relatively to the said axis of bore depending upon the rate of azimuth traversing.

4. In fire control apparatus for a gun mounted for traversing its axis of bore in azimuth about the train axis of the gun and provided with a panoramic telescope supported on the said gun mount with its eye piece fixed to maintain its portion of the line of sight parallel to the said axis of bore, a device for introducing angle-oflead correction between the said axis of bore and the said line of sight depending upon the rate of target movement and its range, comprising, in

r combination, a gyroscope mounted with its axis of precession coincident with the said train axis of the gun and operatively connected to the objective piece of the said panoramic telescope, whereby the traversing of the gun together with the said angle-of-lead device in azimuth tracking will cause a turning of the said frame on its horizontal frame axis in response to the precessional turning of the gyroscope, the said frame shaft transmitting the said frame turning to the said objective piece of the panoramic telescope, whereby the line of sight is turned relatively to the said axis of bore depending upon the rate of azimuth traversing and means to regulate the speed of the gyroscope wheel according to the range of the tracked target, whereby the said precessional effect of the said gun traversing, the said responsive frame turning, the said objective piece turning and the said line of sight will be varied in proportion to range.

5. In re control apparatus for a gun mounted for traversing its axis of bore in azimuth and provided with a panoramic telescope supported on the said gun mount with its eye piece fixed to maintain its portion of the line of sight parallel to the said axis of bore, a device for introducing angle-of-lead correction between the said axis of bore and the said line of sight depending upon the apparent angular rate of target movement and its range, comprising, in combination, a gyroscope operatively connected to the objective piece of the panoramic telescope and adapted to turn the same in accordance with the rate of azimuth traversing of the gun, and means for regulating the speed of the gvroscope according to the range of the tracked target.

6. In re control apparatus for a gun mounted for azimuth traversing and provided with a sighting mechanism, an angle-of-lead device comprising, in combination, a gyroscope operatively connected to the said sighting mechanism to compensate the same according to rate of target movement, and means for regulating the speed of the gyroscope according to the target range.

WILLIAM F. TUFTS. 

